Here is the full list of all 48 Afterthought achievements.
Clear all levels with an F time
Clear all levels with an E time
Clear all levels with a D time
Clear all levels with a C time
Clear all levels with a B time
Clear all levels with an A time
Clear all levels with an S time
Beat all story levels
Beat the 1. Boss without taking Damage
Beat the 2. Boss without taking Damage
Beat the 3. Boss without taking Damage
Beat the 4. Boss without taking Damage
Beat the 5. Boss without taking Damage
Beat the 6. Boss without taking Damage
Beat the 7. Boss without taking Damage
Beat the 8. Boss without taking Damage
Clear all Levels without taking damage
Clear all Levels without touching the Floor
Clear all Levels without using Skills
Clear all Levels in Hard Mode
Be faster than 100 m/s
Be faster than 150 m/s
Be faster than 200 m/s
Be faster than 250 m/s
Make it through the first Tutorial
Make it through all Tutorials
Beat all S Time Dev Ghosts
Perform 20k Slide-Offs
Use Wind on the Ground or on Walls 20k times
Destroy 20k Blue Objects with Bolt
Pass through 20k Echos
Perform 20k Teleportations
Beat a Level in under 5 Seconds
Beat a Level in under 10 Seconds
Find a peaceful way to de-escalate any Boss Fight
Find all hidden locations
Reach a Counter value of 100
Stay in the Air for 3 Minutes
Attack 100k Blue Objects
Block 100k Red Objects
Destroy an object that is 100 m away from you
Play a level with every possible skill combo
Clear all Speedrun Modes in the game
Clear the game in Speedrun Mode under 20 Minutes
Clear the game in Speedrun Mode using only one Skill
Write BADASS with your scores in Speedrun Mode
Beat all Training Challenges
Beat all Training Challenges with one second remaining